Classification: Malveae

The tribe Malveae is a division of subfamily Malvoideae of the angiosperm family Malvaceae. It appears to be a well defined group,
characterised by absence of staminodes (which are reduced to apical teeth
terminating the staminal column elsewhere in Malvoideae), by a schizocarpous
fruit (except in Plagianthus, Bastardia and
Bastardiopsis), and by the number of branches of the style equalling the
number of carpels. (The capsular fruit of Plagianthus might be
homologous to a mericarp in other genera of Malveae, arising by reduction of
the number of mericarps to 1, rather than to the capsule of Hibisceae and
Gossypieae. This is supported by the asymmetrical nature of the capsule.)
Malveae has about 1000 species, in 71 currently recognised genera.

Historically the phylogeny of Malveae has been poorly known. Many traits
have been used in classification, such as the base chromosome count, whether
the schizocarp is capitate or verticillate, whether an epicalyx is present or
absent, whether the stigmas are capitate or decurrent, whether the mericarps
are dehiscent or indehiscent, whether the mericarps are single or multi-celled,
or whether the mericarp cells are single or multi-seeded. The classification
obtained depends on the weight given to the individual traits.

I had been investigating the phylogeny myself by combining published DNA
sequences, for the internally transcribed spacers (ITS1 and ITS2) and 5.8s RNA
loci of the nuclear ribosomal DNA,from the relatively large ITS (nuclear
ribosomal DNA) data set for Malveae available at EMBL, arising from several independent
studies, but this has been mostly superceded by a paper by Tate el al [3] combining several of those studies and adding additional
sequences filling in most of the gaps in coverage. The description given here
follows that paper.

Historically Malveae has been divided into several tribes. Three genera -
Malope, Kitaibelia and Palaua - were placed in the tribe
Malopeae, on the basis of bearing capitate, rather than verticillate,
schizocarps. The remaining genera have sometimes been divided between 2 tribes
– Malveae and Abutileae – or between 2 or 3 subtribes within Malveae
sensu lato. (The subtribes would be Malvinae, Abutilinae and Sidinae,
but can be found in older literature as (Eu)Malvae, Abutileae and Sideae.)
Malvinae was distinguished from Abutilinae and Sidinae by the presence of
decurrent as opposed to apical stigmas, and Abutilinae from Sidinae by the
possession of multi-ovular carpels. Kearney introduced a subtribe
Corynabutilinae for those genera with bilaterally decurrent stigmas
(Corynabutilon and Neobaclea), in which he
was followed by Hutchinson [4]. Asa Gray suggested a
subtribe Plagianthinae for Plagianthus and related
genera.

These divisions are not supported by DNA sequence data. Malopeae is nested
within Malveae, and is polyphyletic. Abutilinae, with or without Sidinae, is
also polyphyletic, or at best paraphyletic.

The Malveae is also divided informally into smaller groups of genera, or
alliances. The alliances given in Kubitzki and Bayer [1],
based on earlier work by Bates (1968), Bates and Blanchford (1970), and Fryxell
(1988, 1997), and their contents, are as follows.

Within the Malvaceae Pages I retain a division into subtribes Malvinae and
Abutilinae, but with different bounds to the classical definitions. The
Abutilinae contains the Abutilon, Gaya, Anoda,
Plagianthus and Batesimalva alliances. The Malvinae
contains the Malacothamnus, Malvastrum, Kearnemalvastrum,
Sphaeralcea, Modiola, Malope, Anisodontea,
Malva and Sidalcea alliances.

Abutilinae lack an epicalyx (except for Malvella), and have
bilaterally decurrent (Corynabutilon, Neobaclea) or capitate
stigmas. However these characteristics are insufficient to define the group, as
secondary loss of the epicalyx has also occurred several times in Malvinae, and
capitate stigmas is an ancestral trait also retained in many taxa in Malvinae.
Pendulous ovules are also characteristic of the Abutilinae, but are also found
in pluri-ovulate species of Anisodontea.

The Plagianthus alliance, combined with the South American genus
Sidasodes and 2 species of Sida, forms the basal lineage in
Abutlinae, and is the strongest candidate for recognnition as another
sub-tribe. (Asa Gray suggested a sub-tribe Plagiantheae – Plagianthinae in
modern orthography – to hold the genera of the Plagianthus alliance,
and elsewhere the family Phillipodendreae (Phillipodendraceae) was introduced,
presumably for these genera.) They differ in having the style divided for the
greater part of its length, and hence also in having a short staminal column.
However they agree with Abutilinae in lacking an epicalyx and in having
pendulous ovules.

The following observations can be made from the work of Tate et al [3]

The Batesimalva alliance is polyphyletic

The Gaya alliance is polyphyletic, Lecanophora and
Cristaria not being closely related to Gaya, the former
forming the second basalmost lineage in Abutilinae, and the latter being
nested within the Abutilon alliance, together with elements of the
Batesimalva alliance.

Sidasodes belongs to Abutilinae, rather than to the
Sphaeralcea alliance, and is related to the Plagianthus
alliance.

The Abutilon alliance is paraphyletic with respect to Gaya
and the Anoda and Batesimalva alliances.

Neobrittonia belongs in Abutlinae, rather than in the
Malacothamnus alliance.

Sida and Dendrosida are paraphyletic. There is a well
defined group consisting of species of Sida and Dendrosida,
but other species of Sida fall into various locations in
Abutilinae.

Sidalcea and Callirhoe are not closely related. Their
introrsely decurrent stigmas, and tendencies towards the loss of the
epicalyx and to gynodioecy or dioecy, would seem to be homoplasious. I
interpret the chromosome counts for Sidalcea as representing
diploid, tetraploid and hexaploid members of a series with x=5, and
those for Callirhoe as representing a tetraploid and octoploid
members of a series with x=7, with derived x=15 species,
rather than as hexaploid members of a x=5 series, with derived
x=14 species. I therefore propose separate Sidalcea and
Callirhoe alliances.

The sister group to Sidalcea seems to be Eremalche (which
is consistent with distributional and ecological data), and I therefore
transfer this from the Sphaeralcea alliance to the Sidalcea
alliance. (The shared x=5 base chromosome count in the Sidalcea and
Sphaeralcea alliances appears to be convergent.)

The sister group to Callirhoe seems to be Napaea. This is
consisted with chromosome number data (I interpret the data for
Napaea as x=15), with distributional data, and with Napaea's
dioecious habit. I therefore transfer Napaea from the
Sphaeralcea to the Callirhoe alliance.

The Malva alliance is paraphyletic with respect to the
Malope alliance. Alcea, Althaea are related to
Kitaibelia, and Malva and Lavatera to Malope.
These two groups may be sister to each, but this is weakly supported, and
for example either could be more closely related to the Callirhoe or
Anisodontea alliances. I prefer to split the Malva alliance
into Malva and Althaea alliances.

Sphaeralcea, Nototriche and Tarasa, form a clade.
The former two genera are nested within the last.

Malacothamnus chiliensis is not closely related to the remaining
species of Malacothamnus, but instead to 3 species of Tarasa.
All 4 species have a base chromosome count of 12 (other species of
Tarasa have a count of 10). The genus Andeimalva [2] has been introduced for these 4 species. Introducing
this genus resolves the paraphyly of Tarasa with respect to
Sphaeralcea, but Nototriche remains nested within
Tarasa.

“Urocarpidium albiflorum” nests with Fuertesimalva,
rather than Tarasa, which would make Urocarpidium the correct
name for this genus, rather than Fuertesimalva, unless it be divided
into two genera. (“Urocarpidium albiflorum” is relatively
isolated compared with the remaining species of Fuertesimalva.)

The following other observations can be made.

The traditional division of species between Lavatera
and Malva is incorrect. This is discussed further on the page on the
Malva alliance.

Hybridisation observations suggest that section Hirsutae of
Althaea belongs in the Malva, rather than the Althaea
alliance. A poster at IOPB 2004 presents ITS data confirming this, which is
discussed further on the page on the Malva alliance.